package com.bobbygu.libnet.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


public class MD5Util
{

	protected static char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a',
			'b', 'c', 'd', 'e', 'f'};

	protected static MessageDigest messagedigest = null;

	static
	{
		try
		{
			messagedigest = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException e)
		{
			e.printStackTrace();
		}
	}

	public static String getFileMD5String(File file)
			throws IOException
	{
		FileInputStream in = new FileInputStream(file);
		FileChannel ch = in.getChannel();
		MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
		messagedigest.update(byteBuffer);
		return bufferToHex(messagedigest.digest());
	}

	public static String getMD5String(String s)
	{
		return getMD5String(s.getBytes());
	}

	public static String getMD5String(byte[] bytes)
	{
		messagedigest.update(bytes);
		return bufferToHex(messagedigest.digest());
	}

	private static String bufferToHex(byte bytes[])
	{
		return bufferToHex(bytes, 0, bytes.length);
	}

	private static String bufferToHex(byte bytes[], int m, int n)
	{
		StringBuffer stringbuffer = new StringBuffer(2*n);
		int k = m+n;
		for(int l = m; l<k; l++)
		{
			appendHexPair(bytes[l], stringbuffer);
		}
		return stringbuffer.toString();
	}

	private static void appendHexPair(byte bt, StringBuffer stringbuffer)
	{
		char c0 = hexDigits[(bt&0xf0) >> 4];
		char c1 = hexDigits[bt&0xf];
		stringbuffer.append(c0);
		stringbuffer.append(c1);
	}

	public static boolean checkPassword(String password, String md5PwdStr)
	{
		String s = getMD5String(password);
		return s.equals(md5PwdStr);
	}

}